(1) Field of the Invention
The present invention relates to a process for enhanced oil recovery from subterranean liquid hydrocarbon or oil wells which usually have undergone primary liquid hydrocarbon (oil) removal and are pressure depleted. In particular the present invention relates to the injection of highly compressed cooled exhaust gas from an internal combustion engine into an injection well in a gas bearing strata so as to be directed downwardly to solubilize and drive the liquid hydrocarbons from an oil bearing strata to a separate production well. Also the present invention relates to the recycling of the exhaust gas removed from the production well with the oil into the injection well.
(2) Description of Related Art
A general discussion of enhanced oil recovery (EOR) is set forth in Kirk-Othmer Edition 17 168-174 (1982). The goal of EOR is to extract oil which is trapped in the sedimentary rock of the subterranean reservoir. The rock can be sandstone or carbonates, such as dolomite. Commonly, gases are used as a solvent and/or as a driving fluid. Carbon dioxide is usually used as the oil miscible, driving gas and nitrogen is an immiscible driving gas.
Prior art literature in enhanced recovery is as follows: Stoesppelwerth, George P., Oil and Gas Journal, 68-69 (Apr. 26, 1993); Shelton, Jack L., et al., Journal of Petroleum Technology, 890-896 (1973); Bardon, C. P., et al., Society of Petroleum Engineers, U.S. Department of Energy, SPE/DOE 14943, 247-253 (1986); Palmer, F. S., et al., Society of Petroleum Engineers (SPE 15497), (1986); Monger, T. G., et al., SPE Reservoir Engineering, 1168-1176 (1988); Haines, H. K., et al., International Technical Meeting, Paper #CIM/SPE (1990); Johnson, H. R., et al., SPE/DOE 20269, pages 933-939 (1990); Monger, T. G., et al., SPE Reservoir Engineering, 25-32 (1991).
Patents which are related are U.S. Pat. No. 3,295,601 to Santourian; U.S. Pat. No. 3,411,583 to Holm et al; U.S. Pat. No. 3,547,199 to Fronina et al; U.S. Pat. No. 3,841,406 to Burnett; U.S. Pat. No. 3,995,693 to Cornelius; U.S. Pat. No. 4,465,136 to Troutman; U.S. Pat. No. 4,509,596 to Emery; U.S. Pat. No. 4,656,249 to Pebdani et al; U.S. Pat. No. 5,381,863 to Weaner; U.S. Pat. No. 5,402,847 to Wilson et al; U.S. Pat. No. 5,065,821 to Hang et al; U.S. Pat. No. 5,413,177 to Horn; U.S. Pat. No. 5,725,054 to Shays et al; and U.S. Pat. No. 5,663,121 to Moody.
The prior art has described the use of exhaust gases from internal combustion engines for increasing hydrocarbon production. Illustrative is a system described by Stoesppelwerth in Oil/Gas Journal, April 1993 and an Internet listing by Energy, Inc. of Tulsa, Okla. In the latter case, a single well is used and a primary purpose is to unplug the openings in the production well. U.S. Pat. No. 4,465,136 to Troutman describes the use of exhaust gas with water flooding around the injection production well. The gas pressure in the reservoir is cycled between about 150-300 pounds/m2, which is relatively low, and is referred to as xe2x80x9chuff""n-puffxe2x80x9d. U.S. Pat. No. 5,381,863 to Wehner the carbon dioxide is initially immiscible in the oil at low pressures during injection and miscible at high pressures during extraction from the well.
U.S. Pat. No. 5,065,821 to Huana et al describes lateral drilling for gas injection. There is no use of any plugs in the wells and the well openings for injection and extraction are at the same level. U.S. Pat. No. 5,725,054 to Shayeai et al descries a method using steps of carbon dioxide injection separate from nitrogen injection.
There is a need for a more reliable method for the production of oil from pressure depleted reservoirs.
It is therefore an object of the present invention to provide an improved method for enhanced oil recovery from a subterranean well. In particular, the present invention relates to a method which is relatively economical and reliable. Further, it is an object of the present invention to provide a method which is environmentally sound. These and other objects will become increasingly apparent by reference to the following description and the drawings.
The present invention relates to a method for enhanced recovery of hydrocarbons containing oil from a subterranean hydrocarbon bearing strata comprising the steps of:
(a) providing an exhaust gas from an internal combustion engine, which gas is compressed by a compressor connected to the engine motor, wherein the gas consists essentially of nitrogen and carbon dioxide;
(b) injecting the exhaust gas from the compressor into an injection well and from the injection well into a gas bearing strata which is above the hydrocarbon bearing strata, without injection of the exhaust gas directly into the hydrocarbon bearing strata from the injection well which increases pressure in the oil bearing strata; and
(c) recovering the hydrocarbons and the exhaust gas from a production well in the hydrocarbon bearing strata.
Further the present invention relates to an oil producing well system for enhanced recovery of hydrocarbons including oil from a subterranean bearing strata which comprises:
(a) an injection well for injecting a compressed exhaust gas from an internal combustion engine, which is connected to a compressor for the exhaust gas, into a gas bearing strata which is above the hydrocarbon bearing strata, without injection of the exhaust gas directly into the hydrocarbon bearing strata from injection well;
(b) a production well in spaced relationship to the injection well and extending into the hydrocarbon bearing strata for recovering the exhaust gas and hydrocarbons from the hydrocarbon bearing strata; and
(c) a separation facility above the production well for separating the hydrocarbons from the exhaust gas.